Ok, reading the BBC here and they’re talking about an experiment where fusion was obtained through the use of soundwaves. Or maybe not. The argument as put by the BBC is that of the detection of neutrons with respect to some flashes of light not adding up.
Why don’t they just make the experiment bigger in order to measure quantity of energy created? I don’t understand what the heck the deal is with respect to neutrons etc, and given the seemingly small scale of the experiment involved, it just seems that it would solve a heck of a lot of trouble if it was just scaled up.
Also, isnt energy creation vs used a better determinant?
Sounds like Pons and Fleischmann all over again.
Taleyarkhan’s 2004 paper reports that his current set-up is producing neutrons at a rate of about 400000 neutrons a second. Back-of-the-envelope suggests this corresponds to a power output of less than a millionth of a watt.
You could possibly conceive of scaling the volume up by about a million, but you’d still only be producing a watt or so and it’s probably non-trivial to reliably measure even that in an apparatus of the size that’d be involved.
Not to mention such an experiment being correspondingly that much more expensive to build and operate.
Because there’s no way neutrons could be produced in the apparatus except by some sort of nuclear reaction.
That assumes that Taleyarkhan is seeing neutrons - whether he is or not is what the arguments have been about.
It may not be possible to scale up the experiment; it’s based on using focused sound waves to resonate and collapse a little bubble in a fluid; I’m pretty sure it only works because the bubble is a) small enough to be collapsed by the energy delivered by the sound waves, b) small enough that it doesn’t break up into a number of bubbles and c) small enough that the viscosity of the fluid doesn’t allow it to quickly float out of the point where the sound waves are focused.
As far as I can tell, the claim that fusion is occurring is the only novel thing about the experiment; everything else has been done before and is understood - this guy has just come along, produced the normal flashes of light from sonoluminescence, fudged his neutron detection data (a la Pons & Fleischmann) and made a couple of bold claims. That’s all. Probably.
No fusion reaction products detected, but collapsing argon bubbles in H[sub]2[/sub]SO[sub]4[/sub] reach 20000°K.
I believe it was those guys, Suslick et al, who pretty much said that fusion inside the bubbles is not going to happen. I haven’t read the journal article yet (actually, I’m still trying to find, anybody have a link?), but they were able to measure the actual amount of energy or something… I really would like to find the article. Anyway, for more info on this, look up Suslick. His article in the July 2002 Nature was the one that Squink’s number comes from.
I watched the BBC Horizon programme on it last week and one of the interesting things they revealed is that the experiment in question supposedly needs bubbles of a very precise size; how do they form these bubbles? Using a radioactive (neutron) source; how do they detect if the experiment is performing fusion? by looking for neutrons.
Anyone see a potential problem here?
Here’s a press release from RPI referring to a paper published on Physical Review E (although in a title and abstract search I couldn’t find that they actually published anything) and here’s an abstract from Annales de la Fondation Louis de Broglie (warning: PDF format) that argues for some relation to the Casimir effect to explain the fusion reaction. (I’m not familiar with the peer-review process or esteem of Fondation Louis de Broglie, so take it for what it’s worth.)
I’ve heard a bit about this but never paid more than cursory attention to it. Even if the effect is real, it doesn’t appear to be amenable to scaling up to anything like usuable power-generating quantities. It may be novel (or it may be drivel) but I don’t think anyone is promising it to power a car to the moon and back on a gallon of heavy water.
Well, that’s not quite fair. I mean, certainly you have to subtract off the externally-contributed neutron flux, but that’s no different in principle than any other extra biasing value to be considered. The experimenters have tried to consider this by making control measurements (measuring the neutron flux with deuterated and nondeuterated acetone, and with and without the ultrasound used to control the bubble collapse, for example) to get an idea of the noise floor. They also claim to have found other signatures of fusion (gamma and tritium production). I don’t know enough about nuclear chemistry to know if they’ve covered all the likely sources, let alone to be able to vet their experimental apparatus, but it’s not quite like a perpetual-motion machine with a hidden battery.
The PRE cite is Phys. Rev. E 69, 036109 (2004), by the way.
Thanks for the cite, Omphaloskeptic. Now I’ll have to go over to the Milliken Library and see if I can find it. And then try to make sense of it. :dubious: We’ll see how far I get.
I think you should be able to download the PDF from anywhere on campus through the library’s website.